This invention relates to a fuel injection pump, and more particularly to an apparatus and method for controlling fuel injection timing of a fuel injection pump of the distribution type for use in diesel engines, using a control unit having a microcomputer.
It is well known that various types of fuel injection pumps are employed for supplying fuel into cylinders of a diesel engine. Particularly, fuel injection pumps of the distribution type are widely used because of their simple structure and small size. The fuel injection pumps are arranged so as to convert the rotation of a drive shaft of the pump to the reciprocation of a plunger by a roller ring, a face cam and so on so that fuel is supplied under pressure into cylinders of a diesel engine by the plunger.
On the other hand, it is generally required that fuel injection pumps supply fuel into cylinders of a diesel engine in the most beneficial timing according to the number of rotations of the engine for increasing the engine performance. Therefore, fuel injection pumps are provided with various types of control systems for controlling fuel injection timing.
In conventional fuel injection pumps of the distribution type, a feedback control system is generally used as a control system for controlling fuel injection timing, and, for example, is arranged such that the position of a timer piston, which is detected as an actual timing of fuel injection, is adjusted to a desired or reference position. In the feedback control system, a differential transformer or the like, which is expensive, is used for accurately detecting the position of the timer piston. Furthermore, as is described in Japanese Laid-open Patent Application No. 55-54642, there is provided a control system of fuel injection timing having a detector which detects the rotational position of a roller ring by tracing the roller ring. However, in the case that the control system is employed for controlling fuel injection timing, it will be required that the roller ring is formed in a particular shape.
On the plus side, the above-mentioned conventional devices are being appraised successfully at a site to accurately output information relating to an actual timing of fuel injection. However, on the other hand, the devices are generally expensive.
Unlike a carburetor and the like in a gasoline engine, a fuel injection pump in a diesel engine weighs on the total cost of a diesel engine. Therefore, it is desired that fuel injection pumps are produced at a low cost.